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EAI TR-20 Analog Computers

H

hexsane

Experienced Member
Joined
Mar 4, 2009
Messages
385
Location
Omaha, NE USA
These have been sitting in a bin in Omaha for a while. I thought they were some early type of electronics trainer. I found out in another thread here what they actually were. Although having the computers is pretty cool finding the maintenance manual sitting under them was even better. These things are heavy! If you have ever picked up a standard table top 9-track drive (not the slim model) the weight and size is roughly equal. Now I need to get some help to get them out of the trunk of the car and into the house.

tr20s.jpg

tr20-1.jpg

tr20-2.jpg

tr20stuff.jpg

tr20maintman.jpg
 
I have an EAI user manual for the 1000 (later machine) I can email you a copy if you like. I got it online, but can't remember where. there's a lovely analogue computing web-museum at "vaxman's" site http://analogmuseum.dyndns.org/english/

That may be where I got the manual.
I wish I'd picked up the analogue plotter when I got my machine. There is also a multi-channel vector scope made by eai that would be great to watch output on. I guess I'll just have to use my scope.
 
Wow, these are really cool. It looks like you even got a spare
program board. You got a few patch cords but you'll find you
never have enough of these. Pomona make nice ones but the prices
will make you gag.
The idea is that you can create most any simulation that can
be written as a differential equation and the occational non-linear
function. The trick is to convert the differential equation into a
intergral equation ( get out you old calculous book ). Once that
is done, you can then create the simualtion.
A greate example is the bouncing ball as in the Heathkit EC-1
manual. There are a few web pages as well. Always look for the
specific computers names as well as generic "analog computer".
Dwight
 
These would be from the 1970's, no? I seem to recall that EAI was still pumping these out (as well as a few hybrid models) then. So, depending on one's age, this may not qualify for a "system older than you".
 
Right, some of you there's no hope lol (j/k!!) I was originally trying to find the date before I posted but easily was distracted by who knows what. The quick thing I read just said "60's" hence my comment. Per this site http://userwww.sfsu.edu/~hl/c.EAI.html looks like 1964. Pretty good age, and analog computing is such an awesome concept. That's funny that it really and rightfully dwarf the Altair, etc in age and significance. I imagine it may be more difficult to appease the better halves out there though with the lack of blinken lights.

Also, Dwight I remember you posting that to another person here (was it Bill or Evan maybe?) that I think came across one of these and started to try and get it running.
 
Nice gadgets. I remember taking a class that required lab sessions with the analog computer. It was a lot of fun patching the program in and setting the veinier pots. What a thrill to see the answer come out on the plotter and to change a parameter and see the immediate response.

It's been so long, I have some questions. Where are the Op Amps? I seem to remember Op Amp symbols on the board. How are the initial conditions set up? And how did one start the simulation?
 
We have a good-condition TR-20 in our museum here in New Jersey, with a thorough complement of manuals and patchboards. It is VERY heavy!

Here is a BIG picture .... zoom in and you can see every atom. :)

http://snarc.net/tr20.jpg
 
barythrin said:
Right, some of you there's no hope lol (j/k!!) I was originally trying to find the date before I posted but easily was distracted by who knows what. The quick thing I read just said "60's" hence my comment. Per this site http://userwww.sfsu.edu/~hl/c.EAI.html looks like 1964. Pretty good age, and analog computing is such an awesome concept. That's funny that it really and rightfully dwarf the Altair, etc in age and significance. I imagine it may be more difficult to appease the better halves out there though with the lack of blinken lights.

Also, Dwight I remember you posting that to another person here (was it Bill or Evan maybe?) that I think came across one of these and started to try and get it running.
Click to expand...

Hi
Bill has a small SystronDonner. It is an analog computer but not the
same as a EAI with 20 amps. I have a Comdyna 20 but there are a number
of features, especially the non-linear functions, that it doesn't have.
I also have a Hearhkit EC-1. It has 9 amps but no non-linear functions.
You have to add you own diode to be the ground surface in the bouncing
ball program.
The Comdynas were mostly sold to schools while the EAIs were mostly
used for industrial purposes.
Many games can be programmed on analog computers. Things like
lunar lander and pong come to mind.
Dwight
 
I used to use a bunch of EAI computers at work, controlling valves on rockets during ground testing. My favorite was a later model that used a digital computer as a sort of programmable patchboard. You never had to go looking for the bent leaf on that one!

The small ones are great fun, too. Looks like quite a find.

Now you need a few boxes of patch cords.
 
Hi
Wondered if you've had a chance to play with your TR-20s yet?
I was just looking at ebay and there is an EC-1 that is already
at $700 with no knobs and no component patch parts?? It
isn't even tested to work.
Dwight
 
Hi, Everyone. I just joined this forum. I worked for EAI back in the '60s, and used their analog computers until 1983. I am a friend of Bernd Ulmann (vaxman) who has a personal analog computer museum at www.vaxman.de. He is trying to save all the analog computers, and recently acquired an EAI Pacer 700 which is a large scale 100 volt machine. This may be the only 100 volt solid state machine that has survived.

I would like to acquire an analog computer if any of you know where there is one that is available.

B
 
Hi
I've not got any for sale but expect to have some fun
with mine once I get my Nicolet DSO working. My analog
computer and the DSO should make a perfect combination.
I see these come up often on eBay. Many less than $60.
Analog computers go for much higher prices lately.
Dwight
 
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